Tidal deformability of white dwarfs in Eddington-inspired Born-Infeld gravity
Abstract
We compute the static quadrupole Love number k2 and the dimensionless tidal deformability Λ of cold white dwarfs in Eddington-inspired Born-Infeld (EiBI) gravity. Matter couples to the physical metric while perturbation equations are solved in an auxiliary metric, so the physical tidal field near the surface depends on derivatives of the equation of state. This dependence is regular for a surface polytropic index 1<Γenv<3/2, but not for the Γ= 5/3 Chandrasekhar equation of state. The mechanism, an algebraic map between the metric that carries perturbations and the metric that matter feels, is common to Palatini-type theories, so the same type of surface condition should apply to tidal calculations in this wider class. We use thermodynamically consistent envelopes that exactly reach zero enthalpy. At five masses from 0.6 to 1.3 Msun and five sampled Born-Infeld couplings κ, with |κ|≤5×106 m2, the EiBI-GR differences are approximately linear in κ. The largest absolute fractional shifts are 3.89× 10−5 in the stellar radius R, 4.09× 10−5 in k2, and 2.36× 10−4 in Λ. Across nine envelope models, half the spread of each quantity relative to the baseline envelope is at most 0.0186 in R and 0.0857 in k2, but only 3.02× 10−5 in Λ as the changes in k2 and R5 largely cancel. A high-precision calculation shows that the envelope dependence of the EiBI-GR difference in Λ is small. Half the spread of this difference ranges from 1.067× 10−12 to 6.208× 10−11 over the 20 nonzero mass-coupling points.
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BibTeX
@misc{pradhan2026tidal,
title = {{Tidal deformability of white dwarfs in Eddington-inspired Born-Infeld gravity}},
author = {Santanu Pradhan and Tapobrata Sarkar},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.19629},
eprint = {2610.19629},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.19629},
}
RIS
TY - UNPB
TI - Tidal deformability of white dwarfs in Eddington-inspired Born-Infeld gravity
AU - Santanu Pradhan
AU - Tapobrata Sarkar
PY - 2026
DA - 2026/10/14
PB - arXiv
DO - 10.48550/arxiv.2610.19629
UR - https://arxiv.org/abs/2610.19629
AB - We compute the static quadrupole Love number k_2 and the dimensionless tidal deformability Λ of cold white dwarfs in Eddington-inspired Born-Infeld (EiBI) gravity. Matter couples to the physical metric while perturbation equations are solved in an auxiliary metric, so the physical tidal field near the surface depends on derivatives of the equation of state. This dependence is regular for a surface polytropic index 1<Γ_env<3/2, but not for the Γ= 5/3 Chandrasekhar equation of state. The mechanism, an algebraic map between the metric that carries perturbations and the metric that matter feels, is common to Palatini-type theories, so the same type of surface condition should apply to tidal calculations in this wider class. We use thermodynamically consistent envelopes that exactly reach zero enthalpy. At five masses from 0.6 to 1.3 Msun and five sampled Born-Infeld couplings κ, with |κ|≤5×10^6 m^2, the EiBI-GR differences are approximately linear in κ. The largest absolute fractional shifts are 3.89× 10^−5 in the stellar radius R, 4.09× 10^−5 in k_2, and 2.36× 10^−4 in Λ. Across nine envelope models, half the spread of each quantity relative to the baseline envelope is at most 0.0186 in R and 0.0857 in k_2, but only 3.02× 10^−5 in Λ as the changes in k_2 and R^5 largely cancel. A high-precision calculation shows that the envelope dependence of the EiBI-GR difference in Λ is small. Half the spread of this difference ranges from 1.067× 10^−12 to 6.208× 10^−11 over the 20 nonzero mass-coupling points.
ER -